Portable blower with blower tube noise reduction

ABSTRACT

The present invention provides for noise reduction during operation of a portable blower by reducing the noise or acoustic energy escaping from the housing outlet and blower tube. The noise reduction is achieved by placing sound absorbing material in the blower tube. The sound absorbing material may include flared upstream and downstream ends to reduce turbulence. The sound absorbing material may be held within the blower tube by an insert frame such that substantial portions of the sound absorbing material are exposed to air passing through the blower tube. Also disclosed is a sound absorbing insert that can be placed within an existing blower tube to retrofit portable blowers with noise reduction technology.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/090,481, titled PORTABLE BLOWER WITH NOISE REDUCTION, filedon Jun. 4, 1998, now U.S. Pat. No. 5,979,013, which is acontinuation-in-part of U.S. patent application Ser. No. 09/037,491titled PORTABLE BLOWER WITH NOISE REDUCTION, filed on Mar. 10, 1998, nowabandoned, both of which are hereby incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to the field of portable blowers. Moreparticularly, the present invention provides a portable blower includingsound absorbing material within the blower tube to reduce the amount ofnoise or acoustic energy escaping from the blower.

BACKGROUND

Portable blowers are in common use by homeowners and professionals toremove debris from yards and driveways without water or other equipmentsuch as rakes or brooms. The portable blowers can be powered by eitheran electric motor or a gas-powered motor. Furthermore, some of theblowers can be converted into vacuum units in which leaves or similardebris can be vacuumed into a bag or other container.

When operated as blowers, the units provide a sweeping action using afast moving stream of air produced by an impeller rotating within thehousing of the blower. The impeller draws air into the unit through aninlet and forces the air out of the unit through an outlet. An exhaustor blower tube is typically fitted over the outlet to contain the airstream to a nozzle at the end of the blower tube. The length of theblower tube typically allows a user to stand and hold the portableblower while locating the nozzle near the ground. In addition, thenozzle outlet opening is typically smaller than the outlet at thehousing to increase the velocity of the air as it exits the nozzle atthe end of the blower tube.

Although portable blower units provide the ability to move debriswithout using water, rakes, brooms, etc., they can raise issuesregarding noise during use. Because the blowers are typically usedoutside, the noise generated by the blowers has typically been ofreduced importance. With their increasing use, however, the noisegenerated by the blower units has been receiving heightened attention.Furthermore, the noise generated by the portable blowers is increasingas the blowers become more powerful to improve their ability to movedebris.

One attempt at addressing noise generated by portable blower unitsdisclosed in U.S. Pat. No. 5,195,208 (Yamami et al.) is directed atblowers designed to be carried on the backs of the operators. The noiseproduced by the blower unit is reduced by essentially placing the unit,including the motor and the blower portions, between sound absorbingsheets located on at least two sides and the rear of the unit. Althoughthis approach may be helpful in reducing the noise generated bybackpack-mounted blower units, it does not address the needs ofhand-held blowers, nor does it specifically address the noise generatedat the inlet of air into the housing or at the exit of air from theoutlet of the housing.

SUMMARY OF THE INVENTION

The present invention provides for noise reduction during operation of aportable blower by reducing the noise or acoustic energy escaping fromthe blower. Noise escaping from the blower tube is attenuated throughthe use of sound absorbing material located around a passageway withinthe blower tube. By exposing substantial portions of the inner surfaceof the sound absorbing material to the air moving through thepassageway, acoustic energy contained within the airstream can beabsorbed by the sound absorbing material.

The sound absorbing material and inserts of the present inventionpreferably attenuate acoustic energy while limiting negative impact onairstream velocity and/or volume. In preferred embodiments, the soundabsorbing inserts may include flared upstream and downstream ends tomaintain airstream velocity and/or volume as air passes through thepassageway formed in the sound absorbing insert.

In preferred embodiments, the sound absorbing material is provided inconnection with an insert that can be located within a blower tube. Evenmore preferably, the insert can be inserted into existing blower tubesnot originally designed to accept sound absorbing inserts.

In one aspect, the present invention provides a portable blower having ablower tube attached to a housing outlet. Sound absorbing material islocated within the blower tube and includes an inner surface locatedabout a main passageway for air moving through the blower tube, whereinat least about 50% or more of the inner surface of the sound absorbingmaterial located about the main passageway is exposed to the air movingthrough the main passageway.

In another aspect, the present invention provides a portable blowerhaving a blower tube attached to a housing outlet. The blower tubeincludes an upstream end and a nozzle with the blower tube tapering fromthe upstream end to the nozzle. A sound absorbing insert is locatedwithin the blower tube and includes an inner surface located about amain passageway for air moving through the blower tube. The soundabsorbing insert is retained within the blower tube by an interferencefit with the tapering blower tube.

In another aspect, the present invention provides a portable blowerhaving a blower tube attached to a housing outlet. A sound absorbinginsert is sized to fit within the blower tube and includes a mainpassageway for air passing through the sound absorbing insert. The soundabsorbing insert also includes sound absorbing material having an innersurface located about the main passageway, wherein at least about 50% ormore of the main passageway is open to the inner surface of the soundabsorbing material.

In another aspect, the present invention provides a portable blowerhaving a blower tube attached to a housing outlet. A sound absorbinginsert is sized to fit within the blower tube, the sound absorbinginsert including an insert frame having an upstream end, a downstreamend, and at least one support strut between the upstream end and thedownstream end. The sound absorbing insert also includes a mainpassageway for air passing through the sound absorbing insert, the mainpassageway located between the upstream end of the insert frame and thedownstream end of the insert frame. The sound absorbing insert alsoincludes sound absorbing material having an inner surface located aboutthe main passageway between the upstream end of the insert frame and thedownstream end of the insert frame. A substantial portion of the mainpassageway is open to the inner surface of the sound absorbing material.

In another aspect, the present invention provides a sound absorbinginsert for a blower tube of a portable blower. The sound absorbinginsert includes an insert frame having an upstream end, a downstreamend, and at least one support strut between the upstream end and thedownstream end. The sound absorbing insert also includes a mainpassageway for air passing through the sound absorbing insert, the mainpassageway being located between the upstream end of the insert frameand the downstream end of the insert frame. The sound absorbing insertfurther includes sound absorbing material having an inner surfacelocated about the main passageway between the upstream end of the insertframe and the downstream end of the insert frame, wherein a substantialportion of the main passageway is open to the inner surface of the soundabsorbing material.

In another aspect, the present invention provides a method ofattenuating the acoustic energy produced by a portable blower having ablower tube. The acoustic energy is attenuated by placing a soundabsorbing insert within the blower tube, the sound absorbing insertincluding an insert frame having an upstream end, a downstream end, andat least one support strut between the upstream end and the downstreamend. The sound absorbing insert also includes a main passageway for airpassing through the sound absorbing insert, the main passageway locatedbetween the upstream end of the insert frame and the downstream end ofthe insert frame. The sound absorbing further includes sound absorbingmaterial having an inner surface located about the main passagewaybetween the upstream end of the insert frame and the downstream end ofthe insert frame, wherein a substantial portion of the main passagewayis open to the inner surface of the sound absorbing material.

These and other features and advantages of the articles according to thepresent invention are discussed more completely below in connection withillustrative embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one portable blower according to thepresent invention.

FIG. 2 is an exploded perspective view of the blower tube and plenumassemblies of the blower of FIG. 1.

FIG. 3 is a perspective view of a portable convertible blower/vacuumassembly according to the present invention set up for operation in thevacuum mode.

FIG. 4 is a front view of the plenum 60 attached to the blower of FIG.1.

FIG. 5 is a right side view of the plenum of FIG. 4.

FIG. 6 is a left side view of the plenum of FIG. 4.

FIG. 7 is a top plan view of the plenum of FIG. 4.

FIG. 8 is a bottom plan view of the plenum of FIG. 4.

FIG. 9 is a rear view of the plenum of FIG. 4.

FIG. 10 is a cross-sectional view of the plenum of FIG. 7, taken alongline 10--10 in FIG. 7 (the view including an impeller for illustrativepurposes).

FIG. 11 is a cross-sectional view of the plenum of FIG. 7, taken alongline 11--11 in FIG. 7.

FIG. 12 is perspective view of one blower tube insert frame according tothe present invention.

FIG. 13 is a perspective view of a sleeve of sound absorbing materialmounted on the blower tube insert frame of FIG. 12 (the frame depictedin phantom).

FIG. 14 is a plan view of the blower tube insert frame of FIG. 12.

FIG. 15 is a partial cross-sectional view of a blower tube insertmounted in a blower tube as depicted in FIG. 1, the cross-section beingtaken along line 15--15 in FIG. 1.

FIG. 15A is a perspective view of an alternative sound absorbing insertframe design.

FIG. 15B is a perspective view of another alternative sound absorbinginsert frame design.

FIG. 15C is a perspective view of another alternative sound absorbinginsert frame design.

FIG. 16 is a schematic diagram illustrating operation of one impellerwithin the housing of a blower according to the present invention.

FIG. 17 is a front view of an alternate plenum 160.

FIG. 18 is a rear view of the plenum of FIG. 17.

FIG. 19 is a top view of the plenum of FIGS. 17 and 18.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

The present invention provides noise reduction for portable blowers.Preferably, the noise or acoustic energy escaping from the air outlet ofthe housing is reduced, although it will be understood that noisereduction at both the inlet and the outlet is also beneficial and withinthe scope of the present invention.

The desired acoustic energy frequencies of interest in connection withthe present invention will preferably be those at about 20 kHz and belowbecause those frequencies are typically audible to the human ear. Awider range of desired frequencies may, however, be considered for avariety of reasons, e.g., if the blowers will be used around animalswith the ability to hear higher frequencies.

Although the present invention is described below with respect tohand-held electric blowers, it will be understood that the presentinvention can also be used in connection with backpack style blowers, aswell as hand-held blowers. Furthermore, blowers according to the presentinvention can be powered by gas or electric motors.

In most aspects, one preferred portable blower of the present inventionis constructed in a manner similar to the blower described in U.S. Pat.No. 5,560,078 (Toensing et al.), which is hereby incorporated byreference in its entirety. As a result, many of the construction detailsdisclosed in that patent will not be repeated here.

FIGS. 1 and 2 illustrate one embodiment of a portable blower accordingto the present invention. The blower includes a housing 10 and animpeller 30 mounted for rotation within the housing 10 about axis ofrotation 26 during operation. The impeller 30 preferably includes aplurality of lower blades 32 and upper blades 38 designed to move air asthe impeller 30 rotates within the housing 10.

The preferred portable blowers according to the present invention arehandheld during operation and the housing 10 of the blower of FIG. 1includes a handle 16 to facilitate operation of the blower by anoperator. It will be understood, however, that the present inventioncould also be adapted to blowers designed for use as a "backpack" styleblower.

The housing 10 includes a housing inlet 40 located directly below theimpeller 30 and an outlet 50 located generally to the side of theimpeller 30. As the impeller 30 rotates during operation, air is drawninto the housing 10 through the inlet 40 and exits the housing 10through the outlet 50. To facilitate the movement of air, the housing 10includes a scroll 12 (see FIG. 16) about which air is moved by theimpeller 30 until it reaches the outlet 50 of the housing 10, where itexits the housing 10. In other words, air is drawn into the housing 10by the impeller 30 through the inlet 40 and moved about the scroll 12 tothe outlet 50, where the air exits the housing 10.

The housing 10 also preferably includes smaller motor air inlets 14located above the motor (not shown). During operation of the blower, airis also drawn through these inlets 14 past the motor to provide coolingduring operation. The air drawn into the housing 10 through the motorair inlets 14 is also moved through the scroll 12 and exits the housing10 through the outlet 50.

FIGS. 1 and 2 also depict a plenum 60 designed to be located over theinlet 50 of the housing 10. The plenum 60 is provided to reduce theamount of acoustic energy escaping from the housing inlet 50 byabsorbing a portion of the acoustic energy escaping from the housinginlet 40 during operation of the blower. In addition, the plenum 60 alsopreferably manages the direction in which the acoustic energy propagatesout of the plenum 60 as discussed more fully below.

Also depicted in FIGS. 1 and 2 is one preferred blower tube 80 attachedto the housing 10 at the outlet 50. The blower tube 80 is preferablydetachably mounted on the outlet 50 of the housing 10 as described inU.S. Pat. No. 5,560,078 (Toensing et al.) and includes an upstream end82 adapted for attachment to the outlet 50 of the housing 10. The blowertube 80 also includes a nozzle outlet 84 through which air directed intothe blower tube 80 from the housing outlet 50 exits the blower tube 80.

A blower tube insert 90 is preferably located within the blower tube 80.The insert 90 is provided to absorb acoustic energy escaping from thehousing outlet 50. One preferred insert 90 illustrated in FIGS. 1 and 2and includes a substantially open frame 92 over which sound absorbingcomponent 94 is located. The blower tube insert 90 will be described inmore detail below.

It is preferred that the blowers with which the plenums and blower tubesof the present invention are used also be convertible to vacuum units asdescribed in U.S. Pat. No. 5,560,078 (Toensing et al.). One blower isdepicted after conversion into the vacuum mode in FIG. 3, where theplenum 60 and blower tube 80 are removed and replaced by a vacuum tubeassembly 2 that removably attaches to the inlet 40 of the housing 10 anda vacuum bag 4 and associated collar 6 that are attached to the outlet50 of the housing 10.

The plenum 60 of the illustrated embodiment provides one means forabsorbing the acoustic energy escaping from the housing inlet 40 of theblower while the blower tube insert 90 within blower tube 80 providesone means for absorbing the acoustic energy escaping from the blower atthe housing outlet 50. Together, the plenum 60 and the insert 90 providea system for noise reduction in portable blowers, although it will beunderstood that either may be used alone. The use of either apparatusalone may be helpful in retrofitting existing blowers with which, e.g.,the plenum 60 would be incompatible but the blower tube insert 90 wouldbe compatible or vice versa. Using either the blower tube insert 90 orthe inlet plenum 60 alone may provide a smaller noise reduction thanusing both devices together, but could be helpful in providing at leastsome reduction in the amount of noise escaping from the blower.

FIGS. 4-9 depict various views of one preferred plenum according to thepresent invention. The illustrated plenum 60 includes a plenum aperture62, a bottom 64 opposite the plenum aperture 62 and a sidewall 66surrounding the plenum aperture 62 and extending towards the bottom 64of the plenum 60. As a result, the plenum 60 defines an interior volume.

The bottom 64 of the preferred plenum 60 includes a series of ribs 65 toprovide increased stiffness and support the plenum 60 (and housing 10 ifattached). It will of course be understood that the support ribs 65 areoptional and that the functions of supporting the plenum 60 andproviding increased stiffness could be provided using a myriad of otherstructures or methods.

FIGS. 4, 5 and 9 depict the plurality of plenum inlet openings 68provided in the sidewall 66 of the preferred plenum 60. As a result,when the plenum 60 is attached to the housing 10 and the impeller 30 isrotated, air is drawn into the plenum 60 through the plenum inletopenings 68. From the interior volume of the plenum 60, the air is drawnthrough the plenum aperture 62 into the housing inlet 40 where it movesthrough the impeller 30 and the scroll 12 in the housing 10 and exitsthe scroll 12 through the housing outlet 50.

FIG. 6 is a side elevational view of the plenum 60 depicting thesidewall 66 on the left side of the preferred plenum 60. The sidewall 66in this view preferably includes a series of elongated depressions 67 toprovide increased stiffness and rigidity to the sidewall 66.

It is preferred that the plenum 60 be removably attachable over thehousing inlet opening 40 using a bayonet-style mount similar to theattachment of the vacuum tube assembly and the air inlet cover describedin U.S. Pat. No. 5,560,078 (Toensing et al.).

The plenum aperture 62 preferably includes a pressure ring 61 adapted tofollow the profile of the impeller blades 32 on the impeller 30. Thatblade profile and cooperating pressure ring 61 are best seen in FIG. 10,a cross-sectional view of the plenum 60 taken along line 10-10 in FIG.7. The view in FIG. 10 includes the impeller 30 to help illustrate therelationship between the plenum aperture 62, pressure ring 61 and theimpeller 30.

The preferred impeller 30 includes lower blades 32 with a lower outsideedge 34 that is angled with respect to the axis of rotation 26 aboutwhich the impeller 30 rotates during operation. It is that blade profilewhich the pressure ring 61 is provided to match. By matching the bladeprofile, the pressure ring 61 improves the efficiency of the impeller 30when the plenum 60 is located over the inlet 40 of the housing 10.Essentially, the pressure ring 61 reduces the amount of air that leaksor spills over from the high pressure side of the impeller blades 32. Asa result, the efficiency of the impeller 30 is improved. In other words,the output air horsepower of the impeller 30 is increased for a givenmotor output (shaft) horsepower.

The preferred impeller 30 includes nine lower blades 32 extending fromthe plate 37 and facing downwards towards the housing inlet 40 whenassembled into the housing 10 (see FIGS. 2 and 10). The impeller 30 alsopreferably includes twelve shorter blades 38 on the opposite side of theplate 37 from the larger blades 32. These blades 38 preferably face theupwards towards the motor (not shown) when assembled into the housing 10(see FIGS. 2 and 10).

Another feature of the preferred plenums 60 illustrated in FIG. 10 isthe bell mouth 63 provided at the entrance to the plenum aperture 62from the interior volume of the plenum 60. The smooth contour of thebell mouth 63 reduces turbulence in the airflow through the plenumaperture 62. That reduced turbulence also reduces the acoustic energygenerated by the air flowing through the plenum aperture 62, therebyfurther reducing the noise generated by the blower during operation. Thebell mouth 63 may also improve the efficiency of the blower by reducingthe flow resistance in the air supply to the impeller 30.

Also depicted in FIG. 9, each of the preferred plenum inlet openings 68includes a pair of louvers 69a and 69b (referred to generally as louvers69) oriented to direct acoustic energy that does exit from the openings68 generally downwards, i.e., away from the plenum aperture 62. In thepreferred plenums 60, it will be understood that only a portion of theacoustic energy exiting from the housing inlet 40 escapes from theplenum 60.

Each pair of louvers 69 preferably includes an upper louver 69a and alower louver 69b. The lower louver 69b of each pair of louvers 69preferably extends further into the interior of the plenum 60 than theupper louver 69a. In the preferred plenums 60 for use with a hand-heldblower as depicted in FIGS. 1 and 2, the louvers 69 preferably direct atleast a portion of the acoustic energy that does escape from the plenuminlet openings 68 towards the ground, where it may be absorbed ordiffusely reflected (which can diminish the intensity of the acousticenergy experienced by the operator and/or others). In addition, byproviding a lower louver 69b that extends further into the plenum 60than the upper louver 69a (in each pair of louvers 69), a significantportion of the acoustic energy reflected from the bottom of the plenum60 is preferably prevented from passing directly through the plenuminlet openings 68 after reflection from the bottom of the plenum 60.

Another feature of the preferred plenum 60 is that the plenum inletopenings 68 are located on the right side and/or rear portion of theplenum sidewall 66 as best seen in FIGS. 4-9. As a result, when theplenum 60 is used on a hand-held blower grasped in the operator's righthand, a significant portion of the acoustic energy is directed away fromthe operator (which can reduce the intensity of the acoustic energy asperceived by the operator).

One preferred embodiment of a plenum 60 according to the presentinvention includes a sound-absorbing element 70 located within thevolume defined by the plenum 60. As illustrated in FIGS. 2, 10, and 13,the sound absorbing element 70 is preferably located opposite from andfacing the plenum aperture 62 (and, therefore, the housing inlet 40 andimpeller 30). In the depicted embodiment, the element 70 is locatedproximate the bottom 64 of the plenum 60.

It is preferred that the sound absorbing element 70 be larger than theimpeller 30 to assist in capturing the acoustic energy escaping from thehousing inlet 40. By larger, it is meant that the sound absorbingelement 70, when projected onto a plane that is perpendicular to theaxis of rotation 26, has a projected dimension in at least one directionon that plane that is larger than the diameter of the impeller 30. Byproviding a sound absorbing element 70 that is larger than the impeller30, the sound absorbing element 70 may capture an increased amount ofacoustic energy as it expands or spreads outward from the impeller 30through the plenum aperture 62.

In the illustrated embodiment, it may be preferred that the projecteddimension (represented by the width (w) in FIG. 10) of the soundabsorbing element 70 be at least about 1.5 times the diameter of theimpeller 30. It may further be preferred that, for oblong soundabsorbing elements such as illustrated element 70, the sound absorbingelement 70 have, in projected dimensions, a width (w) of at least about1.5 times the diameter of the impeller 30 and a length (l) that is atleast about 2 times the diameter of the impeller 30.

The height h of the impeller above the sound absorbing element 70 to theupper edge of the impeller blades 32 at the outside diameter of theimpeller 30 (see FIG. 10) is preferably about 100 millimeters (about 4inches) or more, more preferably about 125 millimeters (about 5 inches)or more. The height h is preferably limited to about 25 centimeters (10inches) or less.

The sound absorbing element 70 may have any desired thickness, providedthat it does not significantly impede the flow of air through the plenumaperture 62 to the impeller 30. Preferably, the sound absorbing element70 has a thickness of about 8 millimeters (3/8 inches) or more, morepreferably about 12 millimeters (about 0.5 inches) or more, and evenmore preferably about 20 millimeters (about 0.75 inches) or more. Thethickness of the element 70 is preferably about 50 millimeters (about 2inches) or less, even more preferably about 38 millimeters (about 1.5inches or less).

It will be understood that the size of the sound absorbing element 70,the height of the impeller 30 above the sound absorbing element 70, andthe thickness of the sound absorbing insert 70 may be related. In oneaspect, as the height of the impeller 30 above the sound absorbingelement 70 is increased, it may be preferred that the size of the soundabsorbing element 70 also increase. One preferred combination of heightof the impeller 30 above the sound absorbing element 70, size of thesound absorbing element 70 and thickness of the sound absorbing element70 is a height h of from about 100 millimeters to about 150 millimetersin combination with a sound absorbing element 70 having a projecteddimension of at least about 1.25 times the diameter of the impeller 30and a thickness in a range of from about 8 millimeters to about 50millimeters.

The sound absorbing element 70 can be made from any material capable ofabsorbing sound such as foams, nonwovens, fabrics, etc. One preferredsound absorbing material is an open cell foam material, e.g., apolyurethane (ester-based) open cell foam having a density of 2 poundsper cubic foot (32 kilograms per cubic meter). The thickness of onepreferred foam sound absorbing element 70 is about 0.75 inches (19millimeters).

Although the preferred sound absorbing element 70 is a separate bodyremovably located within the volume of the plenum 60, it will beunderstood that the sound absorbing element 70 could alternatively befixedly attached to the plenum 60. Also, the sound absorbing element 70could be provide integral with the plenum 60, e.g., insert molded,glued, welded, etc.. In another example, the plenum 60 could bemanufactured of a material in which the density of the material in thebottom 65 of the plenum 60 is varied to enhance the ability of thematerial to absorb acoustic energy at desired frequencies.

The present invention also provides a blower tube that absorbs at leasta portion of the acoustic energy exiting from the blower, particularlythe acoustic energy exiting from the blower through the housing outlet50. Because the blower tube must function to contain and direct theairflow exiting through the housing outlet 50 and absorb acousticenergy, while also withstanding the rigors of normal use, preferredblower tubes according to the present invention may be manufactured fromtwo or more different components. One of the components (a structuralcomponent) may provide structural and other desired properties to theblower tube while another component (a sound absorbing component) mayexhibit the ability to absorb more acoustic energy at desiredfrequencies than the structural component. It may be desirable toinclude more than one sound absorbing component, particularly ifdifferent sound absorbing components are tuned to absorb acoustic energyat different frequencies.

The structural and sound absorbing components may be arranged within theblower tube in any desirable manner. It will be understood that thestructural and sound absorbing components could be, e.g., coinjected,coextruded, over-molded, insert molded, etc., such that the structuraland sound absorbing components were provided integral with each other.The sound absorbing component may be exposed to the interior of theblower tube, it may be encapsulated within the walls of the blower tube,it may be located on the exterior of the blower tube, or it may beprovided in a number of locations on or within the structure of theblower tube. Furthermore, the structural and sound absorbing componentscould be provided separately and either permanently or removably securedtogether.

In another variation, the structural and sound absorbing componentscould be chemically similar but possess different physical propertiesthat affect their relative abilities to absorb acoustic energy of thedesired frequencies, e.g., they could differ in density, stiffness, etc.Other variations in the construction of blower tubes according to thepresent invention will be described with reference to one preferredembodiment described below in connection with the figures.

Regardless of the structural and sound absorbing components used ortheir arrangement, the blower tubes according to the present inventionwill function to contain and direct the airflow exiting through thehousing outlet 50 and absorb acoustic energy, while also withstandingthe rigors of normal use. In addition, any sound absorbing component ispreferably provided in a manner that reduces airflow volume and/orvelocity as little as possible.

One preferred blower tube 80 is depicted in FIGS. 1 and 2 includes anupstream end 82 and a nozzle 84 at the opposite end. It is preferredthat the blower tube 80 taper along at least a portion of its lengthfrom the upstream end 82 to the nozzle 84 to increase the velocity ofair moving through the blower tube 80 from the outlet 50 of the housing10. As a result, the cross-sectional area of the blower tube 80decreases from the upstream end 82 to the nozzle 84. For a more detaileddescription of the construction of one preferred blower tube 80,reference is made to the blower tube discussion in U.S. Pat. No.5,560,078 (Toensing et al.). The preferred blower tube 80 ismanufactured from a structural component.

The blower tube 80 includes a blower tube insert 90 located in theblower tube 80 as illustrated in FIGS. 1 and 2. The insert 90 ispreferably sized for insertion into the upstream end 82 of the blowertube and is maintained in position nearer to the upstream end 82 of theblower tube 80 by an interference fit as the cross-sectional area of theblower tube 80 decreases due to its taper. It will, however, beunderstood that the insert 90 could be located anywhere along the pathof the air exiting from the housing, including, e.g., within the outlet50 of the housing. Furthermore, although the blower tube 80 is depictedas being separate from the housing 10, it may be formed integral withthe housing 10, in which case the blower tube 80 could be an integralextension of the outlet 50.

It is preferred that the blower tube insert 90 be easily inserted intoand removable from the blower tube 80. It is preferred, but notrequired, that the portable blowers used in connection with the presentinvention include a removable blower tube 80 and, furthermore, that theblower tube 80 taper as described above. As a result, assembly of theblower tube insert 90 into the blower tube 80 can be accomplished bysliding the insert 90 into the upstream end 82 of the blower tube 80while it is removed from the blower housing. The insert 90 is preferablywedged within the blower tube 80 because of the decreasingcross-sectional area of the preferred tapered blower tube 80, thusproviding an interference fit. Other techniques of retaining the insert90 within the blower tube 80 may be used in place of the interferencefit or in addition to the interference fit. To remove the insert 90 (ifever necessary), the user might hold the blower tube 80 with theupstream end facing down and tap the blower tube 80 or reach into theblower tube 80 and pull the insert 90 out of the upstream end 82 of theblower tube.

One preferred blower tube insert 90 is depicted in more detail in FIGS.12-15. The blower tube insert 90 includes a frame 92 and a sleeve 94 ofa sound absorbing material that functions as the sound absorbingcomponent located over the frame 92. The frame 92 includes supportstruts 102 that connect the upstream end 96 to the downstream end 98 ofthe insert 90 in addition to defining and maintaining a main passageway91 through the sound absorbing sleeve 94. The main passageway 91 has asmaller cross-sectional area than the portion of the blower tube 80 inwhich it is located to accommodate the thickness of the sound absorbingmaterial 94.

The sleeve of sound absorbing material 94 is preferably retained on theinsert frame 92 by friction, although it may be desirable to useadhesives, mechanical fasteners etc. to retain the sleeve 94 in thedesired position on the insert frame 92.

It is preferred, but not required, that the blower tube insert 90 beremovable from the blower tube 80. For the preferred tapered blowertubes 80, the insert 90 is may be manually removed from the openupstream end 82 of the blower tube 80. By providing the blower tubeinsert 90 as a separate component, existing blower tubes 80 can beretrofitted to include a blower tube insert 90. In addition, the blowertube insert 90 or portions thereof (such as the sound absorbing material94) can be more easily replaced if the blower tube insert 90 isremovable.

Insert 90 includes an upstream end 96, a downstream end 98 and a mainpassageway 91 located between the upstream and downstream ends 96 & 98.Substantially all of the air moving through the blower tube 80preferably passes through the main passageway 91 of the insert 90,although some small portion may leak between the insert 90 and the innersurface of the blower tube 80. Generally, the main passageway 91 can beconsidered to begin at the point at which a substantial portion of themain passageway 91 is open to the sound absorbing material 94 near theupstream end 96 and ends at the point at which a substantial portion ofthe main passageway 91 is open to the sound absorbing material 94 nearthe downstream end 98 of the insert 90. Insubstantial variations in thepoints at each end of the insert 90 at which the sound absorbingmaterial 94 are exposed to the interior of the insert 90 should beconsidered to fall within the scope of the invention as describedherein.

It is preferred that the upstream end 96 be provided with a bell mouth(as illustrated) or other flared shape to reduce turbulence in theairflow moving into the main passageway 91 defined by the insert 90. Theflare provides a smooth transition from the larger cross-sectional areaof the blower tube 80 into the smaller cross-sectional area of the mainpassageway 91. The reduced turbulence may reduce the acoustic energythat could be produced by more turbulent airflow.

It is also preferred that the upstream edge 106 of the upstream end 96closely conform to the interior shape of the blower tube 80 to preventor at least substantially reduce leakage around the upstream end 96during operation. It is further preferred that the upstream end 96 be inactual contact with the interior of the blower tube 80. It is even morepreferred that substantially the entire edge 106 of the upstream end 96of the insert 90 be in contact with the interior of the blower tube 80.

The downstream end 98 of the insert 90 may also be flared to reduceturbulence and the resulting acoustic energy generated within the blowertube 80 by reducing flow separation as air moves out of the smaller mainpassageway 91 of the blower tube insert 90 into the larger blower tube80. In addition, the flared exit of the preferred downstream end 98 ofthe insert 90 may also assist in maintaining airstream velocity and/orvolume to reduce any negative effects the insert may have on blowerperformance.

The downstream edge 108 of the flared portion of the downstream end 98also preferably closely conforms to the interior shape of the blowertube 80 to further reduce turbulence in the flow of air moving throughthe main passageway formed by the insert 90. It is further preferredthat the downstream end 98 be in actual contact with the interior of theblower tube 80. It is even more preferred that substantially the entireedge 108 of the downstream end 98 of the insert 90 be in contact withthe interior of the blower tube 80.

By providing flared upstream and downstream ends 96 and 98 in connectionwith the insert 90, larger portions of the perimeter of the mainpassageway 91 can be opened to the sound absorbing material 94 toimprove sound absorption. Although increasing the amount of soundabsorbing material 94 exposed to the airstream moving through the mainpassageway and providing a main passageway 91 with a smallercross-sectional area than the blower tube 80 may reduce airstreamvelocity and/or volume, those negative effects can be countered byprovided flared upstream and/or downstream ends 96 and 98 on the insert90. As a result, preferred inserts 90 include at least one of, andpreferably both, flared upstream and downstream ends 96 and 98.

The portion of the illustrated insert frame 92 located about the mainpassageway 91 includes a plurality of support struts 102 that are spacedapart to open a substantial portion of the main passageway 91 to thesound absorbing material 94 located about the main passageway 91. As aresult, the air moving through the main passageway 91 during operationis exposed to the sound absorbing material 94. It may be preferred that,along the main passageway 91 between the upstream end 96 and thedownstream end 98 of the insert 90, at least about 50% or more, morepreferably at least about 75% or more, and even more preferably at leastabout 90% or more of the main passageway 91 be exposed to the innersurface 104 of the sound absorbing material 94. Viewed from theperspective of the sound absorbing material 94, it can be said that atleast about 50% or more, more preferably at least about 75% or more, andeven more preferably at least about 90% or more, of the inner surface104 of that portion of the sound absorbing material 94 located about themain passageway 91 is exposed to the air moving through the mainpassageway 91.

In those instances in which the insert 90 is located within a taperedblower tube 80, it is also preferred that the insert 90 also be tapered,i.e., that the cross-section area of the upstream end 96 of the insert90 be larger than the cross-sectional area of the downstream end 98 ofthe insert 90. It may be further preferred that the main passageway 91be tapered, i.e., have a cross-sectional area that decreases from theupstream end to the downstream end.

It will be understood that the design of the support struts 102 providedin the illustrated insert frame 92 represent only one example and thatan insert frame 92 could be provided with support struts 102 in anydesired configuration provided they open a sufficient portion of themain passageway 91 to the sound absorbing material 94. For example, thesupport struts 102 may be insert molded or otherwise formed within thevolume of the sound absorbing material 94.

FIG. 15A illustrates one alternative blower tube insert frame 192 thatincludes an upstream end 196, a downstream end 198 and a plurality ofsupport struts 202 that extend along the main passageway 191 locatedbetween the upstream end 196 to the downstream end 198. Although foursupport struts 202 are illustrated in FIG. 15A, it will be understoodthat as few as one support strut 202 could be provided if the soundabsorbing material (not shown) possessed sufficient structural rigidityto maintain an open main passageway therethrough.

FIG. 15B illustrates another blower tube insert frame 292 including anupstream end 296, a downstream end 298 and a helical support strut 302that coils about the main passageway 291 located between the upstreamend 296 and the downstream end 298. Although only one helical coil isillustrated, it will be understood that more than one coil may be used.If an additional coil is used, it may advantageously coil in theopposite direction from the illustrated coil.

FIG. 15C illustrates another blower tube insert frame 392 that includesan upstream end 396, a downstream end 398, and a plurality of supportstruts 402a and 402b located along the main passageway between upstreamand downstream ends 396 and 398. The illustrated design includes asupport strut 402a extending along the main passageway 391 (which willbe referred to here as the "backbone" support strut 402a). In addition,a plurality of hoop-shaped support struts 402b are located along thebackbone support strut 402a to maintain an open main passageway 391.Although two hoop-shaped support struts 402b are illustrated, it will beunderstood that as few as one or more than two hoop-shaped supportstruts 402b could be used in connection with the backbone support strut402a.

In other sound absorbing inserts according to the present invention, thesound absorbing materials may possess enough inherent structuralstiffness so as to require little or no support about the mainpassageway 91 of the insert 90. As a result, such inserts 90 may notrequire support struts or may require only minimal support. In stillother variations, the insert may include sound absorbing material thatforms a main passageway, the sound absorbing material being bounded onone end by, e.g., a flared upstream end and on the opposite end by,e.g., a flared downstream end.

In the illustrated insert 90 including a frame 92, it is preferred thatthe sound absorbing material 94 be provided in the form of a sleeve. Thesleeve can be made from any material capable of absorbing sound at thedesired frequencies such as foams, nonwovens, fabrics, etc. Onepreferred sound absorbing material is an open cell foam material, e.g.,a polyurethane (ester-based) open cell foam having a density of 2 poundsper cubic foot (32 kilograms per cubic meter). The preferred thicknessof the foam is about 0.25 inches (6 millimeters).

Although it is preferred that the sound absorbing material 94 beprovided in the form of a sleeve extending around the insidecircumference of the blower tube 80, it will be understood that thesound absorbing material could be provided in sheet form or any othersuitable shape, provided that at least a portion of the main passageway91 be lined with the sound absorbing material. It is preferred that thelength of the main passageway 91, i.e., distance between the upstreamand downstream ends 96 & 98, be about 15 centimeters or more. It mayalso be preferred that the length of the main passageway 91 be about 30centimeters or less. The exposed length of the sound absorbing material94 about the main passageway 91 may offer improved noise attenuation byabsorbing a wider range of acoustic frequencies as compared to, e.g.,blower tubes in which a perforated sleeve exposes only small separatedareas to the air moving through the blower tube 80.

Furthermore, the entire inside circumference of the blower tube 80 neednot be lined with sound absorbing material. For example, it may beadvantageous to provide sound absorbing material on only the top and/orbottom surface of a blower tube 80. In another alternative, it may behelpful to provide sound absorbing material on the exterior of theblower tube 80.

Although the sound absorbing material 94 is disclosed as being heldwithin the blower tube 80 by the insert frame 92, it will be understoodthat a separate insert frame 92 may not be required at all. For example,the interior of the blower tube 80 itself could be lined with anappropriate amount of sound absorbing material in a desired shape. Thesound absorbing material could be permanently attached to the blowertube 80, or it could be removable. In another variation, the entirelongitudinal length of the blower tube 80 may be lined with soundabsorbing material that is either fixedly attached to the blower tube orremovable.

FIGS. 17, 18 and 19 depict enlarged portions of an alternate plenum 160and portion of the housing of a portable blower assembly according tothe present invention. In many respects, the plenum 160 is similar oridentical to the plenum 60 described above. The variations between theplenums 60 and 160 can primarily be found in the area where the plenum160 interfaces with the housing of the blower.

As discussed in U.S. Pat. No. 5,560,078 (Toensing et al.), the preferredremovable plenums are attached and locked in place on the blower housingby rotation. With respect to the plenum 160, at least two engagementmembers 180 are provided about the plenum aperture 162. The engagementmembers 180 are designed to fit within slots (not shown) on the housing(see U.S. Pat. No. 5,560,078 for more details on one housingconstruction. After placing the engagement members 180 in thecorresponding slots on the housing, the plenum 160 is rotated about anaxis of rotation 126 to lock the plenum 160 in position on the housing.In the illustrated plenums 60 and 160, the axis of rotation about whichthe plenum is rotated is coincident with the axis of rotation of theimpeller, although it will be understood that the two axes of rotationcould be different. It is also preferred that the engagement members 180have different shapes to prevent attachment of the plenum 160 to thehousing in the wrong orientation.

Because the preferred plenum 160 is locked in position on the blowerhousing by rotational motion, both the housing and the plenum 160 havemating surfaces that generally define a plane perpendicular to the axisof rotation about which the plenum is rotated during locking andunlocking. The preferred plenum 160 includes a mating surface 165 in theform of a generally planar circular ring located about the plenumaperture 162 because the corresponding mating surface on the housing(not shown) is also generally planar. It will, however, be understoodthat the mating surface 165 of the plenum 160 could take any suitableshape based on the shape of the corresponding mating surface of thehousing, for example, the mating surface could be frusto-conical,ribbed, etc. Regardless of the exact shape of the mating surface 165, itwill define a plane that is substantially perpendicular to the axisabout which the plenum 160 is rotated during locking and unlocking ofthe plenum 160. For the purposes of the present invention, the planedefined by the mating surface 165 will be defined as the seal plane 167.

The mating surface 165 on the plenum 160 and the corresponding matingsurface on the housing provides one advantage in that by providing amore effective seal between the plenum 160 and the housing, the escapeof acoustic energy through that interface can be reduced. Anotheradvantage is that the remainder of the upper surface of the plenum 160,i.e., not the mating surface 165, can be provided with a draft anglethat is helpful in separating a molded plenum 160 from its mold duringmanufacturing.

Another feature of the plenum 160 is the orientation of the engagementmembers 180 with respect to the axis of rotation 126. In the plenum 60as described above, the preferred engagement members are orientedgenerally parallel to the seal plane and, as a result, they are orientedgenerally perpendicular to the axis about which the plenum 60 is rotatedduring locking and unlocking (because the seal plane is preferablyperpendicular to the axis of rotation). The engagement members 180 ofthe plenum 160 are, however, offset from a perpendicular orientationwith respect to the axis of rotation 126 of the plenum 160 by an anglea. In one preferred embodiment, the engagement members 180 are orientedat an angle of about 89.5 degrees from the axis of rotation 126 of theplenum 160.

One purpose of the angled orientation of the engagement members 180 isto draw the plenum 160 towards the housing as the plenum 160 is rotatedabout axis 126 during attachment of the plenum 160 to the housing. Wherethe plenum 160 includes a mating surface 165 as seen in FIGS. 17-19, themating surface 165 is preferably forced against the corresponding matingsurface of the housing to provide a tight connection between the plenum160 and the housing.

Illustrative embodiments of the present invention are described above.Those skilled in the art will recognize that many embodiments arepossible within the scope of the invention. Variations and modificationsof the various parts and assemblies can certainly be made and still fallwithin the scope of the invention. As a result, the invention is to belimited only by the claims and equivalents of the invention describedtherein.

What is claim is:
 1. A portable blower having a housing outlet, theportable blower comprising:a blower tube attached to the housing outlet,the blower tube comprising an upstream end and a nozzle, the blower tubetapering from the upstream end to the nozzle; a sound absorbing insertlocated within the blower tube, the sound absorbing insert comprising aninner surface located about a main passageway for air moving through theblower tube, wherein the sound absorbing insert is retained within theblower tube by an interference fit with the tapering blower tube, andfurther wherein the sound absorbing insert tapers from an upstream endof the insert to a downstream end of the insert.
 2. A portable bloweraccording to claim 1, wherein an upstream edge of the sound absorbinginsert closely conforms to the interior shape of the blower tube.
 3. Aportable blower according to claim 1, wherein a downstream edge of thesound absorbing insert closely conforms to the interior shape of theblower tube.
 4. A portable blower according to claim 1, wherein thesound absorbing insert is removable from the blower tube.
 5. A portableblower having a housing outlet, the portable blower comprising:a blowertube attached to the housing outlet, wherein the blower tube comprisesan upstream end and a nozzle, the blower tube tapering from the upstreamend to the nozzle; and a sound absorbing insert sized to fit within theblower tube, wherein the sound absorbing insert tapers from an upstreamend of the insert to a downstream end of the insert and is retainedwithin the blower tube by an interference fit with the tapering blowertube, the sound absorbing insert comprising: a main passageway for airpassing through the sound absorbing insert; and sound absorbing materialcomprising an inner surface located about the main passageway, whereinat least about 50% or more of the main passageway is open to the innersurface of the sound absorbing material.
 6. A portable blower accordingto claim 5, wherein at least about 75% or more of the main passageway isopen to the inner surface of the sound absorbing material.
 7. A portableblower according to claim 5, wherein at least about 90% or more of themain passageway is open to the inner surface of the sound absorbingmaterial.
 8. A portable blower according to claim 5, wherein the soundabsorbing insert further comprises an upstream end and a downstream end,and further wherein the main passageway is located between the upstreamend and the downstream end.
 9. A portable blower according to claim 5,wherein the sound absorbing insert comprises at least one support strut.10. A portable blower according to claim 9, wherein the sound absorbinginsert comprises a plurality of support struts.
 11. A portable bloweraccording to claim 5, wherein the sound absorbing insert furthercomprises a flared upstream end comprising an upstream edge that closelyconforms to the interior shape of the blower tube.
 12. A portable bloweraccording to claim 5, wherein the sound absorbing insert furthercomprises a flared downstream end comprising a downstream edge thatclosely conforms to the interior shape of the blower tube.
 13. Aportable blower according to claim 5, wherein the sound absorbing insertis removable from the blower tube.
 14. A portable blower having ahousing outlet, the portable blower comprising:a blower tube attached tothe housing outlet; a sound absorbing insert sized to fit within theblower tube, the sound absorbing insert comprising:an insert framecomprising an upstream end, a downstream end, and at least one supportstrut between the upstream end and the downstream end; a main passagewayfor air passing through the sound absorbing insert, the main passagewaylocated between the upstream end of the insert frame and the downstreamend of the insert frame; and sound absorbing material comprising aninner surface located about the main passageway between the upstream endof the insert frame and the downstream end of the insert frame, whereina substantial portion of the main passageway is open to the innersurface of the sound absorbing material.
 15. A portable blower accordingto claim 14, wherein the insert frame comprises a plurality of supportstruts.
 16. A portable blower according to claim 14, wherein the soundabsorbing material comprises a sleeve.
 17. A portable blower accordingto claim 14, wherein the blower tube comprises an upstream end and anozzle, the blower tube tapering from the upstream end to the nozzle,and further wherein the sound absorbing insert is retained within theblower tube by an interference fit with the tapering blower tube.
 18. Aportable blower according to claim 17, wherein the sound absorbinginsert tapers from the upstream end of the insert frame to thedownstream end of the insert frame.
 19. A portable blower according toclaim 14, wherein an upstream edge of the upstream end of the insertframe closely conforms to the interior shape of the blower tube.
 20. Aportable blower according to claim 14, wherein a downstream edge of thedownstream end of the insert frame closely conforms to the interiorshape of the blower tube.
 21. A portable blower according to claim 14,wherein the upstream end of the insert frame and the downstream end ofthe insert frame are flared.
 22. A portable blower according to claim14, wherein the sound absorbing insert is removable from the blowertube.
 23. A sound absorbing insert for a blower tube of a portableblower, the sound absorbing insert comprising:an insert frame comprisingan upstream end, a downstream end, and at least one support strutbetween the upstream end and the downstream end; a main passageway forair passing through the sound absorbing insert, the main passagewaylocated between the upstream end of the insert frame and the downstreamend of the insert frame; and sound absorbing material comprising aninner surface located about the main passageway between the upstream endof the insert frame and the downstream end of the insert frame, whereina substantial portion of the main passageway is open to the innersurface of the sound absorbing material.
 24. A sound absorbing insertaccording to claim 23, wherein the insert frame comprises a plurality ofsupport struts.
 25. A sound absorbing insert according to claim 23,wherein the plurality of support struts comprises at least one supportstrut extending along the length of the main passageway from theupstream end of the insert frame to the downstream end of the insertframe.
 26. A sound absorbing insert according to claim 23, wherein thesound absorbing material comprises a sleeve.
 27. A sound absorbinginsert according to claim 23, wherein the sound absorbing insert tapersfrom the upstream end of the insert frame to the downstream end of theinsert frame.
 28. A sound absorbing insert according to claim 23,wherein the upstream end of the insert frame and the downstream end ofthe insert frame are flared.
 29. A method of attenuating the acousticenergy produced by a portable blower having a blower tube, the methodcomprising:placing a sound absorbing insert within the blower tube, thesound absorbing insert comprising:an insert frame comprising an upstreamend, a downstream end, and at least one support strut between theupstream end and the downstream end; a main passageway for air passingthrough the sound absorbing insert, the main passageway located betweenthe upstream end of the insert frame and the downstream end of theinsert frame; and sound absorbing material comprising an inner surfacelocated about the main passageway between the upstream end of the insertframe and the downstream end of the insert frame, wherein a substantialportion of the main passageway is open to the inner surface of the soundabsorbing material.
 30. A method according to claim 29, furthercomprisingattaching the blower tube containing the sound absorbinginsert to a housing outlet of a portable blower.
 31. A method accordingto claim 29, wherein the blower tube tapers along its length from theupstream end to a nozzle, and further wherein the sound absorbing insertis retained within the blower tube by an interference fit with thetapering blower tube.
 32. A method according to claim 29, whereinplacing the sound absorbing insert within the blower tube comprisesinserting the sound absorbing insert into an upstream end of the blowertube.